UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 
BERKELEY,  CALIFORNIA 


THE  CONTROL  OF  THE 
ARGENTINE  ANT 

By  C.  W.  WOODWORTH 


BULLETIN  No.  207 

Berkeley,  Cal.,  October,  1910. 


BERKELEY 

THE  UNIVERSITY  PRESS 

1910 


Benjamin   Ide  Wheeler,   Ph.D.,   LL.D.,   President  of  the  University. 

EXPERIMENT   STATION   STAFF. 
E.  J.  WiCKSON,  M.A.,   Director  and  Horticulturist. 

E.  W.  Hilgard,   Ph.D.,   LL.D.,   Chemist    (Emeritus). 
W.  A.   Setchell,  Ph.D.,   Botanist. 

Elwood  Mead,  M.S.,   C.E.,   Irrigation  Engineer.      (Absent  on  leave.) 

Lerov  Anderson,  Ph.D.,  Dairy  Industry  and  Superintendent  University  Farm   Schools. 

M.  E.  Jaffa,  M.S.,  Nutrition  Expert,  in  charge  of  the  Poultry   Station. 

R.  H.  Loughridge,  Ph.D.,   Soil  Chemist  and  Physicist    (Emeritus). 

C.  W.  Woodworth,  M.S.,   Entomologist. 

G.  W.  Shaw,  M.A.,  Ph.D.,  Experimental  Agronomist  and  Agricultural  Technologist,  in  charge 
of  Cereal  Stations. 

Ralph  E.  Smith,  B.S.,  Plant  Pathologist  and  Superintendent  of  Southern  California  Patho- 
logical Laboratory  and  Experiment  Station. 

F.  T.  Bioletti,  B.S.,  Viticulturist. 

E.  W.  Major,  B.Agr.,  Animal  Industry,  Farm  Manager,   University  Farm,  Davis. 

George  E.  Colby,  M.S.,  Chemist   (Fruits,  Waters  and  Insecticides),  in  charge  of  Chem.  Lab. 

W.  T.  Clarke,  B.S.,  Assistant  Horticulturist  and  Superintendent  of  University  Extension  in 

Agriculture. 
H.  M.  Hall,  Ph.D.,  Assistant  Botanist. 

H.  J.  Quayle,  A.B.,   Assistant  Entomologist,  Plant  Disease  Laboratory,   Whittier. 
John   S.   Burd,   B.S.,  Chemist,   in  charge  of  Fertilizer  Control. 
C.  M.  Haring,  D.V.M.,  Assistant  Veterinarian  and  Bacteriologist. 
W.  B.  Herms,  M.A.,  Assistant  Entomologist. 

H.   A.  Hopper,  M.S. A.,  Dairy  Industry,   University  Farm,   Davis. 
E.   B.   Babcock,   B.S.,   Assistant  Agricultural  Education. 
W.  T.  Horne,  B.S.,   Assistant  Plant  Pathologist. 

J.  H.  Norton,  M.S.,  Assistant  Chemist,  in  charge  of  Citrus  Experiment  Station,   Riverside. 
J.   E.   Coit,  Ph.D.,   Assistant  Pomologist,   Plant  Disease  Laboratory,  Whittier. 
C.  B.  Lipman,  Ph.D.,  Assistant  in  Soil  Bacteriology. 

R.  E.  Mansell,  Assistant  in  Horticulture,  in  charge  of  Central  Station  grounds. 
J.   C.   Bridwell,  B.S.,  Assistant  Entomologist. 
J.  I.  Thompson,  B.S.,  Assistant  in  Animal  Industry,  Davis. 

E.  H.  Hagemann,  Assistant  in  Dairying,   Davis. 

R.  M.  Roberts,  B.S.A.,  Field  Assistant  in  Viticulture,  University  Farm,  Davis. 
Roscoe  Farrar,   B.S.,  Assistant  in  Soils  and  Farm  Crops,   University  Farm,  Davis. 

B.  S.  Brown,  B.S.A.,  Assistant  in  Horticulture,  University  Farm,  Davis. 
Howard  Phillips,  B.S.,  Assistant  in  Animal  Industry,   University  Farm,   Davis. 
L.  M.  Davis,  B.S.,  Assistant  in  Dairy  Husbandry,  University  Farm,  Davis. 

F.  L.  Yeaw,  B.S.,  Assistant  Plant  Pathologist,  Vacaville. 
F.  D.  Hawk,  B.S.A.,   Assistant  in  Animal  Industry. 

T.  F.  Hunt,  B.S.,  Assistant  Horticulturist. 

C.  O.  Smith,  M.S.,  Assistant  Plant  Pathologist,   Plant  Disease  Laboratory.  Whittier. 

E.  H.  Smith,  M.S.,  Assistant  Plant  Pathologist. 

C.  H.  McCharles,   B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 

A.  J.   Gaumnitz,  M.S.,   Assistant  in  Cereal  Investigations,   University  Farm,  Davis. 
S.   S.  Rogers,   Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

P.   L.  McCreary,  B.S.,   Laboratory  Assistant  in  Fertilizer  Control. 

F.  E.  Johnson,  B.S.,  Assistant  in  Soil  Laboratory. 

M.  E.  Stover,  B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 

Charles  Fuchs,  Curator  Entomological  Museum. 

P.   L.  Hibbard,  B.S.,  Assistant  Fertilizer  Control  Laboratory. 

\.    I).    [NGHAM,   Assistant  in   Sylviculture,    Santa   Monica. 

B.  A.  Madson,  B.S.A.,  Assistant  in  Cereal  Laboratory. 
L.  Bonnet,  Assistant  in  Viticulture. 

Walter  E.  Packard,  Field  Assistant  Imperial  Valley  Investigation,   El  Centre 

E.  E.  Thomas,  B.S.,  Assistant  Chemist,  Plant  Disease  Laboratory,  Whittier. 

Mrs.   I).   L.   BUNNELL,  Clerk  to  the  Director. 

W.  H.  VOLCK,  Field  Assistant  in  Entomology,  Watsonville. 

E.  L.   MORBIS,   B.S.,   Field  Assistant  in  PJntomology,   San  Jose. 

.1.   S.   Hr.NTKK,  Field  Assistant  in  Entomology,   San  Mateo. 

John   T.    BEAB8S,  Foreman  Kearney  Park   Station,  Fresno. 

J.  C.    ROPES,   Patron    University  Forestry  Station,  Chico. 

B.  0.  Mi 1. 1. hi;,  Foreman   University  Forestry  Station,  Chico. 


THE  CONTROL  OF  THE  ARGENTINE  ANT 

By  C.  W.  WOODWORTH. 


Two  years  ago  we  reported  the  presence  of  this  insect  in  California 
in  Circular  No.  38  of  this  station.  The  exact  localities  then  known  to 
be  infested  were  East  Oakland,  Alameda,  San  Francisco,  San  Jose, 
Cupertino,  a  point  near  Campbell,  Los  Angeles,  a  point  near  Azusa, 
and  Upland.  At  the  present  time,  through  the  discovery  of  new  locali- 
ties and  the  natural  spread  of  the  insect,  more  than  twice  as  much 
territory  is  known  to  be  involved,  amounting  to  about  1,000  acres  in 
Southern  California  and  in  the  neighborhood  of  4,000  acres  in  the 
central  portion  of  the  State. 

THE  PRESENT  DISTRIBUTION. 

The  East  Oakland  area  includes  also  nearly  all  of  Fruitvale  and 
occupies  all  the  territory  between  the  bay  and  the  hills  as  far  west  as 
Lake  Merritt,  and  there  are  small  outlying  colonies  scattered  through 
Melrose  on  the  one  hand  and  the  Piedmont  section  on  the  other,  with 
one  small  colony  in  the  center  of  Berkeley. 

Alameda  is  nearly  all  occupied  and  there  are  small,  detached 
colonies  on  Bay  Farm  Island.  The  San  Francisco  colonies  are  all 
small  and  scattered,  the  largest  being  at  the  Presidio  entrance.  Small 
colonies  are  also  found  at  Byron  Hot  Springs  and  at  Stockton. 

The  largest  colony  in  the  State  is  in  San  Jose  and  College  Park, 
extending  continuously  in  one  direction  for  three  and  one-half  miles, 
with  many  detached  colonies  within  a  radius  of  seven  miles,  including 
colonies  at  Santa  Clara  and  those  previously  reported  at  Cupertino 
and  near  Campbell. 

Recently  discovered  colonies  in  and  about  Los  Angeles  places  that 
district  well  toward  the  front  as  to  the  amount  of  infested  territory, 
and  five  small  colonies  in  the  neighborhood  of  Riverside  complete  the 
enumeration  of  the  points  of  distribution  at  present  known  and 
mapped. 

During  the  short  time  elapsing  between  the  first  discovery  of  the 
insect  in  the  State  and  the  publishing  of  the  circular  just  alluded  to, 
so  many  localities  were  found  infested  that  we  feared  that  it  had 


54 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


Fig.  1. — The  egg  of  the  Argentine 
ant.     Very  much  enlarged. 


Fig.  2. — A  very  young  larva  of  the 
Argentine  ant.     Very  much  enlarged. 


Fig.  3. — A  full  grown  larva  of  the 
Argentine  ant.     Very  much  enlarged. 


Fig.  4. — The  pupa  of  a  queen  of 
the  common  small  black  ant  (Tapi- 
noma).     Very  much  enlarged. 


Bulletin  207. 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


55 


already  become  a  generally  distributed  insect,  but  we  are  glad  to  be 
able  to  report  that  all  recent  additions  to  the  list  of  known  localities 
are  of  small  extent  and  have  increased  the  area  of  known  infested 
territory  by  a  very  small  fraction  and  with  the  natural  increase  have 
scarcely  doubled  the  area.  It  is  altogether  likely  that  still  other 
localities  will  come  to  light,  but  we  do  not  anticipate  that  any  con- 
siderable additions  will  be  made.  At  the  time  of  the  publication  of 
the  circular  the  exact  extent  of  none  of  the  infested  tracts  had  been 
accurately  determined.  Since  then  we  have  mapped  all  of  the  known 
areas  and  will  present  them  when  publishing  a  detailed  account  of 
our  investigations. 


Fig.  5. — Head  of  a  queen  Argentine  ant.  The  small  eyes  at  the  top  of  the 
head  distinguish  the  queen  from  the  worker.  The  arrangement  of  the  teeth  on 
the  jaw  distinguishes  the  Argentine  ant  from  all  other  species. 


An  interesting  development  of  the  situation  has  been  the  discovery 
of  the  insect  in  South  Africa,  where  it  occurs  in  several  towns 
corresponding  somewhat  with  its  distribution  in  California.  The 
previous  record,  besides  the  native  countries  Brazil  and  the  Argentine 
Republic,  were  the  Madera  Islands,  with  an  area  of  over  500  square 
miles  completely  infested  as  early  as  1898,  and  the  neighborhood  of 
New  Orleans.  In  the  latter  locality  they  were  first  noted  in  1891,  and 
in  less  than  twenty  years  spread  until,  according  to  Professor  Newell 's 
account,  more  than  five  thousand  square  miles  were  occupied,  or  over 
five  hundred  times  as  much  territory  as  is  now  occupied  in  California. 
This  estimate  is  probably  too  large  since  some  of  the  territory  included 
was  not  actually  occupied  by  the  invading  ant,  but  only  had  scattered 
colonies  of  this  species.  Estimated  on  the  same  basis,  the  San  Jose 
colonies  could  be  given  at  from  fifty  to  a  hundred  square  miles  instead 
of  between  three  and  four  actually  covered,  but  in  a  few  years  more 
they  will  undoubtedly  occupy  the  entire  district. 


56 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


/#L 


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Fig.  6. — The  queen  Argentine  ant.     The  small  figure  below  gives  the  natural 
size.     This  is  fully  twice  as  long  as  the  worker. 


Bulletin  207.  THE  CONTROL  OF  THE  ARGENTINE  ANT.  57 


NATURAL  DISTRIBUTION  SLOW. 

A  reassuring  fact  made  evident  by  these  studies  is  that  the  insect 
spreads  very  slowly  when  not  transported  by  human  agencies.  There 
is  probably  no  group  of  insects  less  capable  of  rapid  migration  than 
ants  as  a  class.  There  are  a  few  species,  including  the  Argentine  ant, 
that  have  nesting  habits  rendering  them  liable  to  be  transported 
through  the  channels  of  trade,  but  aside  from  this  no  ant  is  much  of 
a  migrant.  Apparently  the  Argentine  ant  is  unusually  slow  to  occupy 
new  territory.  We  have  carefully  watched  the  spread  of  this  ant  for 
two  years  and  the  average  extension  of  the  colony  has  not  exceeded 
an  eighth  of  a  mile  a  year;  the  spread  depends  primarily  upon  the 
ant  being  carried  by  man.      The  first   writers  upon  this   ant  have 


Fig.  7. — Side  view  of  body  of  queen  Argentine  ant.  The  middle  region  of 
the  body  shows  the  stubs  to  which  the  wings  were  originally  attached. 

expressed  the  opinion  that  the  carrying  of  the  workers  into  a  new 
territory  would  be  sufficient  to  establish  the  insect  there.  It  is  true 
that  workers  live  a  long  while  if  in  numbers.  It  is  likely,  therefore, 
that  crackers,  sugar,  fruit,  fresh  or  dried,  or  any  other  attractive 
substance  will  be  a  ready  means  of  carrying  the  ants  into  a  new 
district  and  that  they  may  live  in  this  new  locality  for  considerable 
time. 

We  have  no  evidence  whatever  that  such  a  transportation  will  be 
sufficient  to  establish  the  insect  in  its  new  home.  The  establishment 
of  a  colony  requires  the  presence  of  an  insect  capable  of  laying  eggs, 
that  is,  a  queen  ant.  To  be  sure  there  seems  to  be  some  evidence  that 
the  workers  of  some  species  of  ants  may  sometimes  produce  eggs  that 
develop  into  males,  but  this  must  be  very  rare  and  if  common  would 
be  of  no  value  in  establishing  a  colony  which  is  not  complete  till  it  has 
a  fertile  queen.  We  have  kept  colonies  in  the  laboratory  at  East 
Oakland  for  months  under  all  kinds  of  conditions  without,  in  any 


58  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

case,  obtaining  any  evidence  of  egg  laying  except  by  queens.  We 
should  judge  that  a  queenless  colony  might  live  for  months  under 
favorable  conditions,  but  ultimately  its  annihilation  is  a  certainty. 

Could  a  colony  be  established  by  workers  alone,  nothing  could  have 
prevented  the  whole  State  becoming  infested  by  this  ant  long  ago. 
The  moving  of  the  queen  is  the  essential  condition  without  which  the 
spread  of  the  insect  is  impossible. 

METHODS  OF  TBANSPOKTATlON. 
The  people  of  the  State  living  beyond  a  few  hundred  feet  from  an 
infested  territory  are  in  no  immediate  danger  of  invasion  of  the  ant 
except  when  at  least  one  queen  with  attendant  workers  are  transported 
by  human  agency.  It  will  be  well,  therefore,  to  indicate  the  ways 
this  may  be  brought  about.     There  seems  to  be  good  evidence  that  in 


Fig.  8. — Face  of  the  queen  of  a  field  ant  (Formica).     Notice  the  position  of 
the  large  eyes.     These  insects  do  not  follow  trails. 

several  cases  the  insects  were  brought  in  manure.  It  is  a  very  common 
practice  to  haul  manure  to  lawns,  gardens,  and  orchards,  and  it  is 
difficult  to  see  how  a  load  could  be  taken  from  an  infested  pile  without 
transporting  many  queens.  It  would  seem  to  be  a  good  policy  to 
prevent  by  stringent  quarantine  the  moving  of  such  material  from 
infested  to  non-infested  territory.  A  most  careful  inspection  should 
also  be  made  of  nursery  stock  from  infested  nurseries,  potted  plants 
of  freshly  dug  stock  from  infested  land,  either  in  the  field  or  from  the 
healing  in  ground,  are  possible  means  of  transference.  Even  when 
there  is  no  earth  left  on  the  roots  the  queen  ant  may  have  found 
temporary  shelter  in  the  packing  material.  Vegetables  are  another 
possible  means  of  transportation.  Ants  are  often  particularly 
abundant  in   potato  fields,  and  queens  could   very  easily  find  shelter 


Bulletin  20' 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


59 


in  bags  and  boxes  of  potatoes.  Household  goods,  food  stuffs,  or  almost 
any  commodity  could  easily  afford  temporary  shelter  for  a  nest  driven 
out  of  the  ground  by  rain  or  irrigation,   if  not  indeed  affording  a 


3    # 

4 


Fig  9. — Worker  of  the  smaller  honey  ant  (Prenolepis) .     Notice  the  shape  of 
the  abdomen. 


permanent  resting  place.  The  point  of  these  remarks  is  that  we  now 
know  enough  of  the  habits  of  the  Argentine  ant  to  make  evident  that 
it  is  the  wisest  course  to  at  once  undertake  rigid  quarantine  measures 


60 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


to  prevent  undue  spread  of  the  pest.  This  is  advisable  whether 
eradication  is  considered  possible  or  not.  We  should  not  allow 
ignorance  or  carelessness  to  spread  the  pest  over  the  State  any  faster 
than  it  will  go  if  left  to  itself. 


AEGENTINE    ANTS    DO    NOT    FLY. 

The  establishment  of  new  colonies,  in  the  case  of  many  species  of 

ants,  is  preceded  by  the  well-known  flight  of  the  young  queens,  each 

going  off  by  herself  and  rearing  a  new  family.      Supposing  that  the 

same  rule  held  in  the  case  of  the  present  species  and  that  the  extension 


2S 


Fig.  10. — Head  of  the  smaller  honey  ant. 

of  the  infested  territory  was  brought  about  in  this  manner,  we  at 
once  endeavored  to  follow  very  carefully  the  development  of  the 
young  queens  in  the  spring  and  to  watch  their  flight  so  as  to  have  a 
good  idea  of  the  range  of  spread  by  this  means.  To  our  surprise, 
however,  while  winged  individuals  were  produced  in  great  quantities, 
both  in  our  laboratory  and  in  the  field,  there  was  apparently  no  flight 
whatever.  Once  or  twice  the  males  came  out  of  the  nests  in  moderate 
numbers  and  fluttered  their  wings,  but  did  not  rise  in  the  air,  and 
the  females  remained  within  the  nest  until  they  had  lost  their  wings 
and  became  egg  producing.  Possibly  under  different  climatic  con- 
ditions from  that  of  East  Oakland  a  flight  might  occur,  but  nothing 
of  the  kind  was  observed  in  San  Jose  by  Mr.  Morris,  or  as  far  as 
I  am  aware  in  any  region  by  anyone. 

These  observations  make  it  very  probable  that  the  danger  of 
spreading  by  the  flight  of  the  queen  ants  is  practically  nothing.  This 
probably  accounts  for  the  very  slow  rate  of  spread  of  this  species  and 
is  an  extremely  hopeful  feature  in  case  eradication  work  is  attempted. 


Bulletin  207. 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


61 


CONDITION    OF    MIGKATION. 

Another  very  hopeful  and  significant  point  in  case  eradication  is 
attempted  is  the  fact  that  the  insect  is  not  liable  to  occupy  new 
territory  except  under  the  press  of  hunger.  Under  the  promptings  of 
hunger,  however,  it  is  very  ready  to  move  and  the  presence  of  a  new 
source  of  supply  may  result  in  the  shifting  of  the  domicile  within  half 
an  hour  or  so  of  the  discovery  of  the  food.  On  the  other  hand,  when 
food  is  sufficient  for  the  ants  of  the  colony  and  no  special  attraction 
exists  a  road  may  furnish  sufficient  barrier  to  prevent  the  spread  of  the 


Fig.  11. — Face  of  Tapinoma  sessile.  This  is  the' ant  most  commonly  confused 
with  the  Argentine  species.  Note  particularly  the  arrangement  of  the  teeth 
on  the  jaw. 

ant  indefinitely.  There  are  many  cases  where  the  ant  has  not  crossed 
the  road  during  the  two  years  it  has  been  under  observation.  It  is 
very  probable,  therefore,  that  a  single  city  block,  surrounded  by  roads, 
may  be  treated  as  an  independent  colony  as  long  as  the  ants  are  not 
more  abundant  in  the  adjacent  blocks  than  the  food  available  wrill 
accommodate,  that  is,  if  poisons  are  used  as  described  below  in  all  the 
adjacent  blocks  to  maintain  the  numbers  sufficiently  small,  no  fear 
need  be  entertained  of  a  reinfestation. 


EEADICATION. 

This  is  a  term  that  many  entomologists  believe  should  cease  to  be 
used  because  they  consider  it  something  that  is  impossible,  and  many 
have  already  expressed  their  conviction  that  this  ant  is  here  to  stay 
no  matter  what  may  be  done  toward  its  destruction.  The  term  has 
been  so  often  used  in  this  State  for  the  partial  destruction  of  an  insect 
pest  that  perhaps  many  do  not  appreciate  that  it  has  never  been 
accomplished  anywhere  in  the  world  after  an  insect  has  secured  the 


62 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


foothold  secured  by  this  ant,  and  cannot  be  accomplished  without  more 
thorough  work  than  has  yet  been  given  in  this  State  or  elsewhere.  It 
is  the  easiest  way,  perhaps,  to  say  that  eradication  is  impossible  and 
not  try,  or  to  reduce  the  numbers  and  call  it  eradication,  but  such  a 
very  small  part  of  the  State  is  now  involved  and  the  insect  is  capable 
of  producing  so  much  damage  and  annoyance  it  would  be  too  bad  not 
to  make  at  least  a  serious  effort  toward  eradication. 


Fig.  12. — Worker  of  Tapinoma  sessile.     Notice  the  top  of  the  abdomen  over 
hanging  the  ' '  hump. ' ; 


In  some  ways  this  insect  is  a  particularly  good  one  with  which  to 
work.  It  is  so  slow  to  spread,  most  of  the  individuals  are  incapable 
of  reproduction.  The  queens  live  in  definite  families  and  are  thus  not 
liable  to  escape  detection,  but  on  the  other  hand  present  some  problems 
of  particular  difficulty  and  require  a  most  careful  study  of  their  life 
and  habits  to  prevent  one  making  fatal  mistakes. 

The  methods  of  eradication  will  not  be  essentially  different  from 
those  available  for  control  work,  with  the  exception  that  some  may 
be  entirely  proper  for  eradication  but  too  expensive  to  be  available 
for  control.  Thus  defoliation  of  the  kind  used  two  years  ago  in  Marys- 
ville  for  the  white  fly  is  justifiable  only  in  an  attempt  at  eradication, 
and  such  treatment  every  few  years  for  control  is  out  of  the  question. 
On  the  other  hand,  spraying  or  fumigation  is  available  for  control 
work,  but  hopeless  for  eradication  for  that  same  insect.  In  work 
directed  against  the  Argentine  ant  we  may  find  the  same  to  hold  or 
we  may  find  that  the  most  available  control  measure  is  at  the  same 
time  the  most  promising  treatment  with   eradication   in   view.     It  is 


BULLETIN   207.  THE  CONTROL  OF  THE  ARGENTINE  ANT.  63 

probable  that  efficient  work  toward  eradication  will  depend  much 
more  upon  the  organization  and  administration  of  the  work  rather 
than 'upon  the  means  employed.  No  matter  how  effective  a  treatment 
may  be,  the  result  will  be  negative  unless  the  campaign  is  so  organized 
that  the  last  individual  queen  insect  is  destroyed.  The  efficiency  of 
the  provisions  for  ensuring  the  death  of  this  last  individual  is  the 
index  of  the  success  of  the  effort.  This  fact  cannot  be  too  strongly 
emphasized.  No  matter  how  effective  a  treatment  may  be  or  how 
thoroughly  it  may  be  applied,  it  fails  if  the  home  of  one  queen  is 


Fig.  13. — Head  of  Dorymyrmex  pyramicus.  This  is  the  most  abundant  ant 
in  the  southern  part  of  the  State.  The  coarse  teeth  on  the  jaws  distinguish 
it  at  once. 


overlooked.  It  is  this  fact  alone  that  makes  eradication  difficult.  We 
know  many  remedies  that  can  be  employed  to  destroy  ants.  We  do 
not  yet  know  what  it  is  wisest  to  employ,  and  it  is  more  than  likely 
that  we  will  find  different  treatments  best  under  different  conditions. 
I  do  not  anticipate  that  this  is  a  case  where  a  specific  will  be  found, 
but  the  work,  like  a  battle,  will  require  the  direction  of  a  resourceful 
commander.  Moreover,  it  is  not  a  work  that  can  be  done  in  a  day, 
but  should  be  undertaken  with  the  idea  that  final  success  will  only 
come  by  destroying  the  insect  step  by  step.  We  now  know  more  than 
forty  separate  colonies  of  the  Argentine  ant.  If  all  were  treated,  and 
though  failure  resulted  in  the  majority  of  cases,  any  success  would 
promise  final  victory  by  continuing  the  fight  along  the  same  line. 

If  the  success  of  the  work  depended  upon  one  general  attack,  I 
would  have  no  confidence  of  victory,  not  because  of  the  inefficiency 
of  the  remedy  employed,  but  because  of  the  difficulty  of  a  perfect 
organization  of  the  effort.  ■>,,,  l0  : 


64 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


HOW    IMPORTANT    ANTS    ARE. 

While  it  remains  a  question  whether  the  Argentine  ant  can  be 
eradicated  in  the  State  at  large,  there  is  but  very  little  doubt  that, 
taken  in  time,  small  colonies  could  be  annihilated,  and  this  raises  the 
question  at  once  as  to  the  importance  of  destroying  them.  In  the 
circular  already  referred  to  we  have  described  very  fully  the  serious- 
ness of  this  insect  in  Louisiana.  Further  study  has  shown  that  the 
danger  due  to  the  direct  attack  of  this  insect  upon  vegetation  is  not 


Fig.  14. — Worker  of  Dorymyrmex  pyramicus.     Notice  the  pyramid  above  the 
base  of  the  middle  and  hind  legs. 


Bulletin  207. 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


65 


as  large  in  this  State  as  the  experience  in  Louisiana  led  us  to  fear. 
In  every  other  respect,  however,  the  Argentine  ant  has  proven  itself 
quite  as  serious  a  pest  as  first  indicated,  and  in  addition  its  insidious 
attacks  upon  bee  hives  has,  at  least  in  one  instance,  put  an  amateur 
beekeeper  out  of  business,  and  in  two  cases  that  have  come  to  our 
attention  have  become  an  equal  menace  in  aviaries  by  the  attacks  upon 
the  nestling,  and  indeed  there  is  considerable  evidence  that  they  will 
have  an  appreciable  effect  upon  native  wild  birds  in  the  same  way. 


Fig.  15. — Head  of  Iridomyrmex  analis. 
Argentine  ant  in  California. 


This  is  the  nearest  relative  of  the 


As  a  household  pest  the  Argentine  ant  certainly  stands  ahead  of 
all  other  species,  and  many  of  the  native  species  are  serious  enough. 
Whenever  the  Argentine  ant  gets  established  it  destroys  all  other 
species  of  ants  and  becomes  much  more  abundant  than  all  the  others 
combined.  Unless  one  uses  remedies  they  become  almost  unbearable 
in  the  kitchen,  and  it  is  probably  very  conservative  to  estimate  that 
the  presence  of  the  ant  reduces  the  commercial  value  of  real  estate  for 
residence  purposes  from  ten  to  twenty-five  per  cent.  Many  cases  have 
come  to  our  attention  of  people  moving  out  of  the  infested  territory 
on  account  of  the  ants  and  of  sales  of  real  estate  falling  through  as 
soon  as  the  prospective  purchaser  discovered  the  presence  of  the  ant. 


NATIVE  SPECIES. 
Often  when  the  Argentine  ant  first  enters  the  house  it  is  not 
distinguished  from  the  native  species,  the  housewife  only  noticing 
that  the  ants  have  become  particularly  annoying  and  do  not  respond  so 
readily  to  remedies.  It  will  be  very  desirable,  therefore,  to  point  out 
the  distinction  between  this  species  and  the  various  native  species 
with  which  it  mav  be  confounded. 


66 


UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 


There  are  some  forty-six  species  of  ants  known  to  occur  in  Cali- 
fornia. These  have  been  divided  into  four  sub-families,  three  of  which 
include  species  that  give  more  or  less  annoyance  in  the  house,  the  fourth 
including  a  single  species  of  the  legendary  ants  so  abundant  and 
troublesome  in  tropical  America,  but  which  is  a  very  rare  insect  in 
California. 


/' 


Fig.  16.— Worker  of  Iridomyrmcx  anaUs. 


BULLETIN   207.  THE  CONTROL  (JF  THE  ARGENTINE  ANT. 


67 


These   sub-families   are   distinguished   by   the    following  key,   the 
figures  will  illustrate  the  characters  mentioned: 

Pedical  one  jointed. 

Labrum  not  reaching  above  the  bases  of  the  antennae, 

Formicinae,  15  species. 
Labrum  extending  up  between  the  antennae,         Dolichoderinae,  5  species. 
Pedical  two  jointed. 

Frontal  ridges  covering  bases  of  antennae,  Myrmecinae,  25  spec:es. 

Frontal  ridges  not  covering  bases  of  antennae, 

Dorylinae,  1  species,  Echiton  calif 'ornicus ,  Mayr. 


r^^rtK 


Fig.  17. — Head  of  a  house  ant  (Monomorium) .  This  ant  is  an  introduced 
species  from  Europe. 

Sub-family  Formicinae. — This  sub-family  is  often  called  Campono- 
tinae  after  its  largest  genus  Camponotus.  There  are  four  genera  in 
California,  distinguishable  by  the  following  table : 

Clypeus  scarcely  any  broader  than  high,  Camponotus 

Distinctly  wider  than  high. 

Clypeal  fossa  distinctly  separated  from  antennal  fossa,  Prenolepis 

Confluent. 

Fourth  joint  of  maxillary  palpi  not  quite  as  long  as  fifth, 

Myrmecocystus 
A  little  longer,  Formica 

The  Carpenter  Ants.  Camponotus. — The  largest  ants  in  California 
are  known  as  the  Carpenter  ants  and  have  sometimes  been  called 
"wood  ants."  They  are  among  the  most  abundant  ants  of  the  moun- 
tains and  foothills  wherever  the  country  is  wooded.  There  are  five 
different  species,  mostly  black  in  color  and  of  large  size.  They  live  in 
rotten  logs  and  stumps  and  are  occasionally  brought  into  town  in  fuel 
and  may  establish  themselves  in  the  woodwork  of  houses.  There  are 
two  or  three  such  colonies  in  Berkeley,  for  instance.  It  is  only  rarely 
that  they  become  very  annoying  and  usually  they  die  out  in  a  few  years 


68 


UNIVERSITY  OP  CALIFORNIA EXPERIMENT  STATION. 


after  they  are  first  introduced.  I  have  never  observed  a  conflict 
between  these  ants  and  the  Argentine  species,  but  there  is  no  doubt 
that  the  Argentines  would  destroy  them  as  they  have  the  other  species, 
even  though  they  are  between  fifty  and  a  hundred  times  as  large. 
Wherever  this  ant  becomes  troublesome  there  is  no  doubt  that  the 
remedies  suggested  for  the  Argentine  would  be  even  more  effective. 


Fig.    18. — Worker   of   the   fungus   growing   ant    (Cyphomyrmex).      The    most 
peculiar  shaped  ant  in  California. 


Field  Ants.  Formica. — I  am  using  this  term  to  designate  the  com- 
monest ants  found  in  the  gardens  and  fields  in  the  Coast  region  of 
California.  These  ants  also  occur  all  over  the  world,  though  in  the 
desert  regions  they  are  nowhere  near  as  abundant  as  the  harvest  ants 
referred  to  below.  Some  five  species  have  been  recorded  in  California, 
ranging  in  color  from  black  to  a  mixture  of  red  and  black.  These 
ants  are  not  infrequent  visitors  in  the  house,  but  always  have  their 
nests  in  the  ground,  where  they  often  remain  during  the  hotter  parts 
of  the  day  though  they  are  active  enough  mornings  and  evenings. 
These  ants  resemble  the  Carpenter  ants  in  not  having  any  definite 
pathways;  they  seem  to  be  guided  entirely  by  sight  in  their  movements 
and  have  the  very  peculiar  habit  of  running  a  short  distance  and  then 
stopping   suddenly   and   after   a   moment   they    rush    forward    again. 


BULLETIN   207.  THE  CONTROL  OF  THE  ARGENTINE  ANT.  69 

These  sudden  stops  and  starts  make  it  quite  difficult  to  follow  one  with 
the  eye.  They  ascend  trees  and  are  perhaps  the  most  constant  visitors 
of  aphis  colonies.  Their  nest  in  the  ground  often  has  many  openings 
and  it  is  rather  difficult  to  locate  them  all  in  the  case  of  plowed 
ground.  Where  the  ground  has  not  been  disturbed,  however,  it  is  very 
easy  to  destroy  the  nest  with  carbon  bi-sulphide,  pouring  in  an  ounce 
or  two  and  closing  up  all  the  openings  with  earth.  In  San  Jose  the 
Argentine  apparently  drives  these  ants  ahead  of  them,  because   all 


Fig.  19. — Side  view  of  body  of  the  fungus  growing  ant 


around  the  territory  infested  by  Argentines  the  black  field  ants  are 
unusually  numerous.  Mr.  Morris,  the  Horticultural  Commissioner  of 
Santa  Clara  County  presented  in  a  paper  at  one  of  the  department, 
conferences,  a  very  entertaining  account  of  battles  between  these  two 
species. 

Honey  Ants.  Prenolepis  and  Myrmecocystus. — The  honey  ants  are 
among  the  most  interesting  members  of  this  family,  but  are  not  very 
commonly  troublesome  in  the  house.  The  characteristic  feature  of 
these  species  is  the  fact  that  certain  individuals  are  converted  into 
living  honey-pots,  the  abdomen  swelling  into  a  balloon-like  structure 
for  the  storage  of  the  secretions  of  plant  lice  which  are  gathered  by 
these  insects.  Prenolepis  imparls  occurs  all  over  the  State,  but  is 
nowhere  exceedingly  abundant.  These  insects  often  close  up  their 
burrows'  and  remain  underground  for  months  at  a  time,  usually 
coming  out  in  the  spring  and  taking  advantage  of  the  great  abund- 
ance of  aphids  that  usually  occur  during  this  season.  A  case  came  to 
my  attention  in  East  Oakland  near  the  ant  laboratory  where  there 
was  no  evidence  of  the  honey  ant  during  the  fall  and  winter,  but 
early  in  the  spring  a  very  populous  colony  opened  up  several  entrances 
and  were  active  several  weeks  before  the  Argentines  finally  annihilated 
them,  occupying  their  burrows.  I  have  found  no  other  species  of  ant 
so  far  inside  the  Argentine  territory,  and  it  is  probable  that  when 
attacked  the  year  before  they  simply  closed  up  their  burrows  and 
lived  on  their  stock  of  food. 


70  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

The  following  list  includes  the  species  of  Formicinae  known  in 
California  belonging  to  the  above  mentioned  genera : 

1.  Prenolepis  imparis  Say. 

2.  Formica  rufa  L.  subsp.  obscuriventris  Mayr,  Var.  integroides  Emery. 

3.  Formica  subpolita  Mayr. 

4.  Formica  tejonia  Buck.?. 

5.  Formica  pilicornis  Emery. 

6.  Formica  rufiventris  Emery. 

7.  Myrmecocystus   melliger  Forel,   subsp.   mimicus  Wheeler   var.   depilis 

Forel. 
Myrmecocystus  melliger  Forel,  subsp.  semirufus  Emery,  var.  testaceus. 

8.  Myrmecocystus  mexicanus  Wesm.  var.  horti-deorum  McCook. 

9.  Myrmecocystus  lugubris  Wheeler. 

10.  Camponotus  levigatus  F.  Smith. 

11.  Camponotus  maculatus  Fabr.,  subsp.  vicinus  Mayr. 

Camponotus  maculatus  Fabr.,  subsp.  vicinus  var.  semitestaceus  Emery. 
Camponotus  maculatus  Fabr.,  subsp.  ochreatus  Emery. 

12.  Camponotus  maccooki  Forel. 

13.  Camponotus  herculeanus   L.,   subsp.   pennsylvanicus   DeGr.,   var.    semi- 

punctatus  Kirby. 

14.  Camponotus  fallax  Nyl.,  subsp.  discolor  Buckley  var.  cnemidatus  Emery. 

15.  Camponotus  hyatti  Emery. 
Camponotus  hyatti  var.  bakeri  Wheeler. 

Sub-family  Dolichoderinae. — This  family  also  consists  of  four 
genera,  as  distinguished  by  the  following  table : 

Scale  of  peliole  almost  hidden  by  overhanging  of  abdomen,  Tapinoma 
Freely  exposed. 

Epinotum  with  a  conical  elevation,  Dorymyrmex 
Not  so  elevated. 

Body  densely  pubescent,  Liometopum 

Body  moderately  hairy,  Iridomyrmex 

Each  is  represented  by  a  single  native  species,  and  the  latter  includes 
the  imported  Argentine  ant.     The  names  are  as  follows : 

1.  Liometopum  apiculatum  Mayr  var.  occidentale  Emery. 

2.  Tapinoma  sessile  Say. 

3.  Dorymyrmex  pyramicus  Eoger  bicolor  Wheeler 

4.  Iridomyrmex  analis  Ern.  Andre. 

5.  Iridomyrmex  humilus  Mayr. 

Liometopum  is  a  very  rare  insect,  but  all  the  other  members  of 
the  sub-family  are  very  common  and  very  annoying  household  pests. 

Tapinoma  sessile  is  the  commonest  little  black  ant  all  over  the  State 
and  is  one  of  the  most  abundant  ants  found  in  the  gardens.  The  fact 
thai  it  is  not  found  commonly  far  away  from  human  habitations  and 
is   not    credited   to  -the    State   in    Dr.    Wheeler's    last    list    of   North 


Bulletin  20' 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


71 


American  ants  would  seem  to  indicate  that  this  insect  is  also  an 
introduced  species.  The  insect  is  about  the  same  size  and  general 
appearance  as  the  Argentine  ant,  but  darker  in  color,  not  quite  so 
active  in  its  motion,  and  is  most  easily  distinguished  from  the 
Argentine  species  by  the  fact  that  it  possesses  a  very  strong  odor 
when  crushed.  This  odor  is  produced  by  a  liquid  secretion  which  can 
be  ejected  from  the  abdomen  as  an  appreciable  drop  and  which  is 
used  in  its  contest  with  the  Argentine  species.  As  long  as  the  supply 
of  this  secretion  lasts  the  Tapinoma  has  no  difficulty  in  keeping  the 


Fig.  20. — Head  of  the  fire  ant  (Solenopsis).  This  is  the  most  troublesome 
species  in  the  San  Joaquin  Valley. 

Argentine  off,  but  after  having  put  four  or  five  Argentines  out  of  the 
combat  in  this  way  finally  the  Tapinoma  is  put  to  rout  and  the 
Argentines  are  invariably  victorious,  because  they  always  attack  in 
sufficient  numbers.  We  have  observed  many  battles  between  these  two 
species  and  the  Tapinoma  is  always  driven  away  from  its  feeding 
grounds  and  its  home  despoiled. 

Most  of  the  ant  remedies  used  along  the  Coast  regions  of  Cali- 
fornia, both  north  and  south,  were  devised  to  control  this  insect,  and 
are  quite  sufficient  but  are  not  so  satisfactory  as  the  arsenic  solution 
described  below  Avhich  was  devised  for  the  Argentine  species. 

Dorymyrmex  pyramicns  bicolor. — This  ant  is  very  slightly  larger 
than  the  Argentine  species,  but  resembles  it  in  many  ways  and  is 
readily  distinguished  by  the  fact  that  the  abdomen  is  of  a  darker  color 
than  the  body,  on  account  of  which  fact  the  name  bicolor  was  given  it. 
This  species  occurs  as  the  most  abundant  ant  in  the  towns  and  road- 
sides in  Southern  California  and  is  the  species  that  the  Argentine  ant 
comes   most   commonly   in    conflict   with    in   that   region.      One    can 


72 


UNIVERSITY  OP  CALIFORNIA EXPERIMENT  STATION. 


observe  almost  continuous  fighting  all  along  the  boundary  of  an 
Argentine  territory  in  that  part  of  the  State  between  these  two  species, 
and  while  the  fight  is  always  long  continued  the  Argentine  gradually 
extends  its  sway,  annihilating  the  Dorymyrmex.  The  Dorymyrmex  is 
one  of  the  most  annoying  house  ants  of  Southern  California  and  that 
region  has  for  years  been  a  very  good  place  for  the  sale  of  ant 
remedies,  chiefly  because  of  this  species.  The  problem  of  its  control 
is  practically  the  same  as  of  the  Argentine  species. 


Fig.  21. — Worker  of  the  fire  ant.  The  small  figures  show  the  difference  in 
size  between  the  largest  and  smallest  workers  of  this  ant. 

Tridomyrmex  analis. — This  ant  is  the  nearest  relative  of  the 
Argentine  species,  belonging  in  fact  to  the  same  genus.  It  is  decidedly 
smaller  than  the  Argentine  ant  and  paler  in  color,  in  fact  is  almost 
yellow.  Its  colonies  may  be  found  intermixed  with  those  of  the 
previous  species  and  its  habits  are  not  very  different.  In  relative 
abundance  it  runs  in  the  proportion  of  about  one  of  Iridomyrmex 
analis  to  ten  of  the  Dorymyrmex  pyramicus,  and  were  it  not  for  the 
Dorymyrmex  would  probably  become  a  very  serious  pest  in  the  house. 

Iridomyrmex  humilis. — This,  the  Argentine  ant,  which  appears 
destined  to  become  the  only  ant  in  California,  is  equally  energetic  as 
a  garden  and  a  house  ant,  and  in  the  latter  capacity  particularly  it 
has  no  equal.     Every  foot  of  space  in  the  house  from  cellar  to  attic  is 


Bulletin  20' 


THE  CONTROL  OP1  THE  ARGENTINE  ANT. 


78 


patrolled  almost  hourly  by  specimens  of  this  species,  and  when  any- 
thing that  is  attractive  to  them  as  food  is  left  exposed  in  an  incredibly 
short  time  thousands  of  these  insects  will  appear  and  occupy  them- 
selves in  conveying  it  to  their  nests.  In  doing  this  they  walk  over 
well  defined  paths  as  do  all  other  members  of  this  sub-family  and  in 
the  case  of  this  species  they  leave  enough  dirt  or  secretions  from  their 
bodies  upon  this  path  to  make  it  distinctly  visible  wherever  they 
continue  to  pass  for  some  time.  Their  persistence  renders  them  par- 
ticularly difficult  to  control,  but  the  methods  which  were  developed 
in  our  investigations  have  proven  quite  satisfactory  and  will  be 
described  below. 


Fig.  22. — Head  of  the  acrobat  ant  {Cremastog aster) 


Family  Myrmicinae. — This  is  the  largest  family  of  ants,  the  genera 
of  which  will  be  distinguished  by  the  following  key : 

Head  with  grooves  behind  the  eyes  to  receive  the  antennae,        Cyphomyrmez 
No  antellal  grooves. 

Antenna  ten  jointed,  Solenopsis 

Eleven  or  twelve  jointed. 

Petiole  articulated  to  the  dorsum  of  gaster,  Cremastogaster 

Attached  at  the  end. 

Club  longer  than  the  remainder  of  the  funiculus,  Pheidale 

Not  as  large. 

Mesoepinotal  suture  distinct. 

Posterior  tibial  spurs  pectinate,  Myomica 

Not  pectinate. 

Eyes  vestigial,  Stenamma 

Eyes  well  developed,  Messor 

Suture  indistinct. 

Last  three  joints  of  antennae  much  shorter  than 

the  remainder  of  the  funiculus,  Pogonomyrmex 

Nearly  as  long. 

Mesoepinttum  spined,  Leptothorax 

Not  spined,  Monomorium 


74 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


The  species  thus  far  credited  to  California  are  as  follows : 
1.  Leptothorax  nitens  Emery  var.  heathi  Wheeler. 
Leptothorax  andrei  Emery. 
Leptothorax  pergandei  Emery. 
Monomorium  pharaonis  L. 
Monomorium  ergatogyna  Wheeler. 
Pheidole  barbata  Wheeler. 
Pheidole  hyatti  Emery. 
Pheidole  californica  Mayr. 
Stenamma  brevicorne  Mayr. 
Stenamma  nearcticum  Mayr. 

Apheanogaster  patruelis  Forel  subsp.  bakeri  Wheeler. 
Messor  stodderdi  Emery. 
Messor  pergandei  Er.  Andre. 

14.  Messor  andrei  Mayr. 

15.  Myrmica  bradleyi  Wheeler. 
Pogonomyrmex  barbatus  F.  Smith  var.  rugosus  Emery. 
Pogonomyrmex  occidentalis  Cresson  var.  subnitidus  Emery. 
Pogonomyrmex  subdentatus  Mayr. 
Pogonomyrmex  californicus  Buckley 
Pogonomyrmex  californicus  subsp.  longinodis  Emery. 
Cremastogaster  lineolata  Say  subsp.   leviscula  Mayr  var.   californica 

Emery. 
Cremastogaster  lineolata  Say  subsp.  coarctata  Mayr. 
Cremastogaster  vermiculata  Emery. 
Solenopsis  aurea  Wheeler 

Solenopsis  texana  Emery  subsp.  catalinae  Wheeler. 
Solenopsis  geminata  Fabr. 
Cyphomyrmex  wheeleri  Forel. 


2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 
13. 


16. 
17. 
18. 
19. 

20. 


21. 
22. 
23. 
24. 
25. 


Fig.  23. — Worker  acrobat  ant. 
often  held  up  over  the  thorax. 


Notice  the  shape  of  the  abdomen,  which  is 


Bulletin  207. 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


To 


The  little  House  Ants.  Monomorium. — These  are  imported  species 
found  chiefly  in  towns  but  not  particularly  abundant.  They  disappear 
completely  on  the  coming  of  the  Argentine  species,  but  the  combat 
has  not  been  observed.  They  will  doubtless  respond  to  the  same 
treatment  as  for  the  Argentine  ant. 

The  Fungus-growing  Ants.  Cyphomyrmex. — But  a  single  rather 
rare  species  inhabits  California.  These  insects  are  very  sluggish  and 
do  not  enter  dwellings  since  they  live  on  a  fungus  that  they  cultivate 
on  the  droppings  of  caterpillars  or  similar  substances. 

The  Fire  Ants.  Solenopsis. — These  ants  resemble  somewhat  the 
Borymyrmex  of  Southern  California  and  occupy  economically  some- 
what the  same  position  in  the  San  Joaquin.  A  striking  difference  is 
the  presence  of  large  headed  soldier  ants  and  a  greater  variation  in 
size  of  the  smaller  ants  of  the  colony  and  their  stinging  proclivities, 
which  gives  them  the  name  of  fire  ants,  makes  them  an  added  nuisance. 
The  ant  is  found  also  in  Southern  California,  but  does  not  there 
become  excessively  abundant.  We  have  not  as  yet  seen  this  ant  in 
conflict  with  the  Argentine  species.  The  ant  usually  has  nests  with  a 
single,  very  definite  opening  and  will,  therefore,  be  very  easily  handled 
by  the  use  of  carbon  bisulphide. 


Fig.  24. — Top  view  of  the  body  of  the  acrobat  ant. 

The  Acrobat  Ants.  Cremastog aster. — A  fairly  common  shining 
black  ant  about  towns;  was  imported  into  this  country  from  Asia  by 
way  of  Europe.  The  above  name  is  suggested  because  of  their  habit 
of  walking  about  at  times  with  their  abdomen  thrown  up  over  their 
back.  The  colonies  are  seldom  very  large;  they  are  rather  sluggish 
creatures  and  not  very  commonly  found  in  the  house.  They  could 
undoubtedly  be  poisoned  in  the  same  way  as  suggested  for  the 
Argentine  ant. 

The  Harvesting  Ants. — The  remaining  six  genera  are  all  harvest- 
ing ants,  so  called  by  the  fact  that  they  collect  seeds  of  plants  and 


76 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


after  sweating  them  in  their  nests  remove  the  chaff  and  pile  it  around 
the  entrance.  They  are  the  commonest  ant  of  the  plains  and  bare 
foothills.  Their  nests  are  most  conspicuous  objects  and  can  be  seen 
for  miles.  Some  of  them,  particularly  those  living  well  up  in  the 
Sierras  build  enormous  mounds. 


Pig.  25. — Worker  of  :i  black  harvester  ant  (Stcnamma  andrei), 


Bulletin  207.         THE  control  OP  THE  ARGENTINE  ant.  77 

The  two  commonest  species  are  Messor  andrei,  a  black  species,  most 
abundant  in  the  foothills,  and  Pogonomyrmex  calif ornicus,  belonging 
chiefly  to  the  plains.  All  these  ants,  living  in  their  conspicuous  nests 
in  the  ground,  are  in  consequence  very  easily  destroyed  by  the  use  of 
carbon  bisulphide.  The  Argentine  ant  seems  to  have  but  little  if  any 
more  difficulty  in  disposing  of  these  large  ants  than  of  their  smaller 
foes. 


Fig.  26. — Head  of  Stenamma  andrei. 


CONTROL    MEASURES. 


Ants  abound  where  food  and  water  are  plentiful.  The  harvesting 
ants  dig  deep  burrows  to  water  and  can  live  where  there  is  no  surface 
water  obtainable,  and  nearly  any  species  becomes  independent  of  a 
natural  water  supply  where  there  are  nectar  secreting  insects,  such 
as  scales  or  plant  lice,  or  where  plants  have  glands  that  secrete  liquid 
material.  The  Argentine  ant  is  incapable  of  digging  for  water  and 
will  probably  never  thrive  in  the  drier  plains.  Where  there  is  no  lawn 
or  growing  plants  about  a  place  a  house  may  become  quite  like  a 
desert  and  be  apparently  deserted  by  ants,  but  when  either  wrater  or 
food  is  about  they  come  trooping  back. 

BARRING    ANTS    OUT. 

Wherever  ants  are  present  it  will  be  desirable  to  keep  food  material 
out  of  their  reach,  placing  everything  in  cans,  jars,  or  tight  boxes  as 
many  campers  do.  Ants  cannot  burrow  through  the  walls  so  it  is  a 
very  simple  matter  to  make  closets  or  cupboards  ant  tight.  The 
use  of  felt  strips  about  door  and  window  and  the  puttying  up  of  the 
cracks  about  the  floor  or  wall  will  accomplish  this  very  effectively. 
Where  ventilation  is  desirable  the  use  of  cloth  instead  of  wire  screens 
will  admit  of  some  air  and  is  entirely  ant  tight.  Small  safes  for  meat 
can  be  made  in  this  way  and  where  out-of-door  cloth  closets  are  used 
in  the  hotter  sections,  consisting  of  a  cloth  covered  space  in  which  the 


78  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

cloth  is  kept  wet  by  a  constant  drip  of  water  it  is  only  necessary 
to  see  that  the  cloth  is  tacked  tightly  all  around  and  that  the  door 
closes  tight  and  the  ants  will  be  effecively  barred  out. 

WATEK    BAEKIERS. 

Perhaps  the  best  known  method  of  barring  ants  out  is  the  water 
barrier,  such  as  is  secured  by  setting  the  table  legs  in  cups  of  water. 
This  is  effective  against  most  ants,  but  the  Argentine  ant  has  no 
difficulty  in  crossing  water.  Oil  they  cannot  pass,  but  it  is  objection- 
able. We  have  found  that  the  addition  of  a  very  small  amount  of 
cresol,  just  enough  to  make  the  water  milky,  renders  water  effective. 


Fig.  27. — Body  of  Stenamma  andrei  from  above. 

The  odor  of  cresol  disappears  in  a  day  or  two  and  the  water  will 
continue  effective  indefinitely.  The  cresol  has  germicidal  qualities 
that  prevent  the  water  from  becoming  foul.  Indeed  the  cresol  water 
makes  possible  the  development  of  a  system  of  ant-proofing  that  is 
thoroughly  practical  and  efficient. 

ANT-PEOOFING. 

The  rendering  of  a  house  ant  proof  may  be  accomplished,  provid- 
ing there  is  a  level  all  around  the  house  where  a  trough  can  be 
fastened  which  can  be  kept  filled  with  cresol  water,  and  providing 
that  the  floor  is  made  ant  tight.  It  is  even  possible  to  allow  for  vines 
on  the  house,  and  still  have  it  tight  by  allowing  a  space  through  which 
the  vine  may  grow,  but  stuffing  it  with  cotton  to  prevent  the  ants 
climbing  up  the  stem. 

A  pantry  can  be  easily  made  ant  proof  by  a  trough  just  above  the 
top  of  the  doors  and  windows  and  the  suspension  of  the  shelves  from 
supports  above  this  line. 

We  have  tried  these  troughs  for  months  under  the  most  severe 
conditions  and  they  have  proven  absolutely  effective  and  they  do  not 
need  attention  more  than  two  or  three  times  a  year. 

The  writer  will  be  very  glad  to  advise  with  anyone  contemplating 
the  ant-proofing  of  houses  or  rooms. 


Bulletin  207. 


THE  CONTROL  OF  THE  ARGENTINE  ANT. 


79 


METHODS    OF    KILLING    ANTS. 

The  methods  thus  far  discussed  have  not  been  directed  toward 
reducing  the  numbers,  but  toward  protecting  the  food  in  the  house 
from  their  attacks.  The  more  direct  methods  of  fighting  ants  are  often 
very  practical. 


Fig.  28. — Worker  of  the  large  red  harvester  ant  (Pogonomyrmex  calif ornicus) . 
These  ants  often  coil  themselves  up  as  shown  when  picked  up. 


DESTBUCTION    OF    NESTS. 

In  the  above  description  we  have  referred  to  the  use  of  carbon 
bisulphide  for  the  destruction  of  nests  of  ants.  In  all  the  species 
where  there  are  large  nests  with  a  single  opening  this  is  by  far  the 
most  satisfactory  treatment.  The  plan  is  simply  to  pour  down  a  few 
ounces  of  carbon  bisulphide,  either  in  the  natural  openings  or  in  holes 
made  by  thrusting  in  a  crowbar  and  covering  everything  wTith  earth. 
The  gas  formed  by  the  evaporation  of  the  carbon  bisulphide  effectu- 
ally destroys  both  young  and  old.  This  method  can  be  applied  to  any 
species  where  the  nest  can  be  discovered,  but  in  the  case  of  the 
Argentine  species  it  becomes  the  least  valuable  of  any  method,  since 
the  nests  are  usually  scattered  almost  everywhere  over  the  whole 
surface  of  the  ground  and  the  treatment  to  be  effective  would  have 
to  include  the  entire  ground  space  for  acres  about  the  house  one 
intends  to  protect. 

There  are  conditions  also  which  render  the  carbon  bisulphide 
treatment  insufficient.     In  our  desert  regions  the  soil  becomes  so  dry 


80  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

and  open  that  the  gas  formed  by  the  evaporation  of  the  carbon 
bisulphide  dissipates  itself  so  rapidly  through  the  soil  that  it  becomes 
practically  impossible  to  destroy  the  whole  nest.  In  these  cases  better 
results  have  been  secured  by  the  use  of  a  solution  of  cyanide  of 
potassium.  This  material  has  been  used  for  several  years  in  the  parks 
at  Denver  as  a  secret  preparation,  and  its  efficiency  was  recently 
independently  discovered  by  Mr.  Woglum  in  Southern  California. 
The  method  consists  simply  in  making  a  rather  strong  solution  of  the 
salt  in  water  and  pouring  it  into  the  holes  in  the  same  way  that  carbon 
bisulphide  is  used,  only  very  much  more  of  the  material  is  applied, 
the  amount  actually  used  of  course  depending  on  the  size  of  the 
colony.  Hydrocyanic  gas  is  liberated  in  the  soil  by  this  means  and 
operates  very  effectively  against  all  ages. 

Another  method  which  we  found  effective  and  cheap  and  free  from 
the  disadvantage  of  using  so  violent  a  poison  as  potassium  cyanide 
was  to  apply  distillate  made  into  a  miscible  oil  and  diluted  with 
perhaps  twenty  times  its  volume  of  water.  To  be  thoroughly  effective 
this  must  be  applied  very  liberally,  soaking  the  ground  well  with  the 
mixture.  When  this  is  done  it  seems  quite  as  effective  as  any  other 
method. 

ANT    POWDEES. 

Numerous  ant  powders  have  been  from  time  to  time  recommended 
for  ants,  many  of  which  are  of  but  little  value,  such  as  borax,  chalk 
and  the  like,  which  when  placed  across  the  path  of  the  ant,  may  cause 
it  to  turn  aside  and  in  the  case  of  some  species  apparently  giving 
some  temporary  relief.  These  have  absolutely  no  effect  against  & 
persistent  ant  like  the  Argentine.  The  most  efficient  powder  is  the 
common  Persian  insect  powder  (pyrethrum),  often  sold  under  various 
names  as  indicating  its  availability  for  use  against  ants.  When  this 
is  applied  liberally  on  the  shelves  in  the  pantry  and  around  the  edges 
of  the  room,  it  sometimes  will  keep  the  insects  away  for  several  days 
when  it  must  be  repeated.  Some  housewives  have  had  very  good 
results  by  putting  out  the  powder  just  after  sweeping  in  the  morning 
and  leaving  it  about  until  the  next  day,  when  the  old  powder  is  swept 
up  and  fresh  material  applied.  It  is  rather  an  expensive  manner  of 
treating  ants,  because  it  must  be  kept  up  continuously,  but  were 
there  no  better  methods  available  it  would  certainly  be  better  than 
to  allow  the  ants  to  have  continued  access  to  the  premises,  and  there 
may  be  times  when  it  may  be  worth  while.  It  will  be  cheaper,  how- 
ever, to  buy  the  insect  powder  rather  than  the  special  preparations 
known  as  ant  powders. 


BULLETIN   207.  THE  CONTROL  OP  THE  ARGENTINE  ANT.  81 


ANT    FLUIDS. 

A  very  common  form  of  ant  remedy  for  sale  in  the  drug  stores 
consists  in  an  alcoholic  solution  of  corrosive  sublimate,  usually 
colored  by  some  coloring  matter  to  disguise  the  nature  of  the  prepara- 
tion. Any  preparation  with  a  strong  odor  of  alcohol  is  quite  certain 
to  be  of  this  character.  The  method  of  applying  is  to  paint  the 
material  about  on  the  shelves;  it  immediately  dries  up  but  leaves  the 
fine  crystals  of  corrosive  sublimate  which  seems  quite  deterent  for 
most  species  of  ants.  The  Argentine  ant  seems  to  be  very  little 
influenced  by  this  poison,  and  in  many  experiments  tried  at  the  ant 
laboratory  lines  of  ants  were  found  re-established  across  the  poison 
inside  half  an  hour  of  the  most  liberal  treatment.  Very  good  results 
have  followed  the  use  of  this  material  against  Tapinoma,  which  is 
often  mistaken  for  the  Argentine  ant,  and  even  in  the  case  of  the 
Argentine  sometimes  temporary  relief  is  secured  where  there  is  nothing 
particularly  attractive  to  the  ants  beyond  the  barrier. 


ARSENICAL    POISONING. 

We  obtained  by  far  the  best  results  by  the  use  of  a  very  weak 
solution  of  arsenic  and  syrup.  Most  of  the  commercial  ant  poisons 
commonly  known  as  ant  pastes  consist  of  arsenic  and  syrup,  but  are 
made  very  strong  in  arsenic.  This  kills  the  foraging  ants  almost 
immediately.  We  found  by  reducing  the  arsenic  to  between  one-fourth 
and  one-eighth  of  one  per  cent,  they  would  take  large  quantities  of 
the  material  to  their  nests  and  feed  it  to  the  young,  and  the  whole 
nest  would  be  killed  by  a  slow  poisoning. 

The  most  convenient  way  of  exposing  the  poison  to  the  ants  is  to 
use  a  large  jar  with  a  perforated  cover  and  within  it  place  a  sponge 
saturated  with  the  arsenic  solution.  The  ants  will  enter  through  the 
perforations  in  the  cover,  fill  themselves  with  the  arsenic  solution  and 
carry  it  to  their  nests.  The  sponge  will  hold  enough  poison  to  require 
two  or  three  weeks  to  empty  it,  and  before  that  time  the  ants  will 
almost  entirely  disappear. 

The  number  of  jars  to  use  will  depend  upon  the  abundance  of  ants. 
In  the  worst  cases  a  half-dozen  jars  will  serve  for  an  ordinary  sized 
house  and  lot,  and  if  the  ants  are  not  very  bad  one  jar  may  be  enough, 
in  such  cases  it  is  well  to  place  it  in  the  pantry  or  kitchen. 

The  same  remedy  can  be  used  for  all  the  native  species  of  ants  and 
will  be  more  effective  against  them 


82  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


EESUME. 

The  Argentine  ant  now  occupies  about  5,000  acres  in  California. 

There  are  more  than  forty  separate  colonies,  varying  from  one  acre 
to  nearly  2,000  acres  in  extent. 

Except  when  carried  by  human  agencies  they  spread  at  about  the 
rate  of  an  eighth  of  a  mile  a  year. 

Manure  and  nursery  stock  are  particularly  liable  to  be  the  method 
of  transportation,  though  they  may  go  with  all  sorts  of  merchandise. 

Natural  spread  is  not  accomplished  by  flight. 

Migration  normally  occurs  when  the  numbers  exceed  .  the  food 
supply. 

Eradication  is  a  possibility  and  should  be  undertaken. 

Importance  estimated  as  a  lowering  of  the  value  of  residence  prop- 
erty between  ten  and  twenty-five  per  cent. 

All  native  species  are  discussed  and  the  treatment  of  each  suggested. 

Control  measures  consist  of  barring  ants  out  and  methods  of  killing. 

The  best  barrier  consists  of  water  treated  with  cresol  and  makes 
possible  a  practical  ant-proofing  of  rooms  or  houses. 

For  many  ants  the  nests  may  be  destroyed  by  the  use  of  carbon 
bisulphide,  potassium  cyanide,  or  oil. 

Ant  powders  and  fluids  are  discussed,  but  a  syrup  containing  a  very 
small  quantity  of  arsenic  is  recommended  as  the  most  available  poison 
and  the  only  really  satisfactory  method  of  killing  the  Argentine  ant. 


